The Human Genome Project and various new technologies linking disease phenotypes with cellular genotypes have ushered in a new era in life science research and personalized medicine. Post-genomic era research promises improved clinical diagnostics, better pharmaceutical products and individualized healthcare. Such research begins with asking a specific molecular question of multiple stored precious biologic solutions containing DNA, cDNA, RNA, protein, or other materials isolated from diseased or normal tissue. Such research therefore requires the precise handling of a large number of samples, preferably in an automated apparatus such as taught by U.S. Pat. No. 6,387,330, which is hereby incorporated in its entirety by reference.
At present, precious DNA and other biologic samples used for such studies are typically maintained in aqueous form with solvents such as pure water or Tris-EDTA at concentrations of the order of ng/μl, and are typically stored in transparent plastic microcentrifuge tubes, either individually or in racks. The precious biologic solutions are stored at temperatures of 4° C. or −20° C., with a small percentage at −80° C. or even in liquid nitrogen. Among many drawbacks of the current practice, contamination, evaporation, and lack of convenient inventory control are prominent.
A first problem is contamination. According to the prior art, each time a precious biologic sample is needed, its container is thawed, the cap is opened, and a manually directed pipette is inserted to aspirate and transfer the desired amount of solution to a separate receptacle. Manual pipetting is prone to accidental placement of a pipette tip into a wrong sample. Even a one percent contamination rate can invalidate results of all subsequent experiments in a given sample and study. Similarly, automated pipetting, which is typically done with 96-well plates, requires prior removal of either a non-sealing plastic closure or an adhesive film to access the solution, which may be repeated many times for a given sample. While removing the seal, the samples may be aerosolized through vibration of the solution, which increases the risk of cross-contamination. This is especially true, for example in 96-well plates, where the samples are close to each other.
A second problem is evaporation. Within the teachings of the prior art, the primary source of evaporation and concentration change, is a lack of robust sealing of most microcentrifuge tubes combined with prolonged air contact because tubes are typically filled to only half height to avoid spillage when inserting a pipette tip. Further, diffusion of water through plastic over long periods of time can also cause changes in concentration. Consequently, investigators often use samples whose precise concentration is unknown concentration, which increases the rate of failed, invalid, or uninterpretable results. Laboratories requiring greater quality control recheck the concentration of the samples prior to each use, a practice that is time consuming, expensive, and also wastes precious biologic materials.
A third problem is oxidation. Exposure to dissolved oxygen may oxidatively damage samples. For example, environmental oxidation of may cause strand breaks in DNA or RNA reducing its quality for subsequent analysis, or may oxidize reactive thiol groups in protein solutions, changing protein reactivity in subsequent assays.
A fourth problem is inventory control. Lack of convenient inventory control is an important limitation of the prior art. The ability to plan new studies is impeded because no convenient standard method currently exists to track and maintain records of sample availability, volume, and concentration. Precious solution inventory management is currently in a state similar to that of major food retailers prior to the introduction of barcode-based inventory management technology.
U.S. Pat. No. 6,037,168 addresses the above-mentioned problems associated with the removal of closures from biological samples, by providing an improved releasable seal. While contamination may be thereby reduced (though not as effectively as where each sample is contained within a separate enclosure) evaporation and oxidation problems persist.
U.S. Pat. No. 5,464,396 teaches a multi-syringe assembly for the storage, mixing, and delivery of a biological multi-component material. This device suffers from at least the drawback that filling is performed by introducing the materials into the open ends of the syringes and sealing the syringes by inserting pistons. This method therefore increases the probability of contamination.
U.S. Pat. No. 6,506,610 teaches an apparatus and method for transferring liquids between receptacles with reduced risk of contamination. The apparatus has a waste chamber, a pipette tip parking chamber and at least one process chamber. However, the apparatus and method suffer from the drawback that they do not solve the problems of evaporation and oxidation because the samples are open to the air.
U.S. Pat. No. 6,357,583 teaches a rotary container for collection, transport, and dispensing of biological samples in which the samples are housed in a plurality of wells arranged in a circle and covered with a rotatable cover having a single opening. The use of this apparatus entails a significant risk of cross-contamination when the cover is moved relative to the samples. Alternatively, where a space is provided between the samples and cover to minimize cross-contamination, evaporation and oxidation may result.
Finally, U.S. Pat. Nos. 6,620,383 and 5,785,926 teach complex apparatuses for dispensing microliter or nanoliter amounts of biological materials. However, these apparatuses are not suitable for low-temperature storage or repeated cycles of freezing and thawing, and are too expensive to be practical in the long-term storage of a large number of biological samples.
In summary, current procedures for precious solution storage and dispensing, whether manual or automated, are susceptible to cross-contamination, evaporation, oxidation, and samples are difficult to track.
There is therefore a need for an improved apparatus and processes that overcome these limitations of the prior art and provide for the inexpensive storage, tracking, and dispensing of precious biologic solutions. Specifically, a need exists for a robust, reliable, and secure long-term storage and precision dispensing system for precious biologic solutions for use in life science research and molecular medicine. These advantages and more will be readily apparent to skilled in the art upon reading the following disclosure and examples.